Taxanes are diterpene compounds which find utility in the pharmaceutical field. For example, taxol analogues containing heterocyclic or cycloalkyl groups on the C-13 sidechain find utility as anticancer agents. Such taxol analogues may be prepared through semi-synthetic routes, particularly by the coupling of .beta.-lactam or open chain intermediates to the taxane core to form a sidechain at C-13. As the stereochemistry of these analogues may affect their pharmaceutical activity, methods allowing efficient stereospecific preparation of the intermediate .beta.-lactam and open chain compounds, as well as the final taxane products, are sought in the art.